Fundus camera imaging is acknowledged to be an important diagnostic tool for detection of various conditions affecting the eye, including diabetic retinopathy and macular degeneration. Various embodiments of fundus imaging apparatus are disclosed, for example in U.S. Pat. No. 5,713,047 (Kohayakawa); U.S. Pat. No. 5,943,116 (Zeimer); U.S. Pat. No. 5,572,266 (Ohtsuka); U.S. Pat. No. 4,838,680 (Nunokawa); U.S. Pat. No. 6,546,198 (Ohtsuka); and U.S. Pat. No. 6,636,696 (Saito).
While these patents attest to continuous improvements in fundus camera design, there are still significant hurdles to widespread acceptance and usability of these devices. Among disadvantages noted with current devices are high cost and complexity, difficulty of operation, large size, and image quality limitations. These disadvantages hinder the successful deployment of fundus cameras in primary care physician (PCP) offices or in medical test labs, where they could be used by a technician having relatively little training in device operation and imaging, to obtain images that can be assessed by specialists at some other location or at some later time.
In order to effect simple operation, it would be advantageous for the fundus imaging apparatus to have an operator interface that provides capable controls for operation, with operator feedback as well as automated response to events such as patient head and eye movement. The fundus imaging apparatus should be comfortable for the patient and allow images to be taken efficiently within a short amount of time, without undue stress on the patient or complexity for the operator.
A further significant disadvantage of existing fundus imaging apparatus relates to the requirement for pupil dilation. For most patients, artificially induced enlargement of the pupil is necessary in order to allow sufficient light into the eye of the patient for fundus observation and image capture. At best, pupil dilation is uncomfortable and at least temporarily unsettling; at worst, dilation can even be dangerous for some individuals. Pupil dilation itself requires a chemical application that can only be administered under the care of someone who is suitably trained and certified. A number of commercially available fundus imaging systems claim to be “non-mydriatic”, that is, operable without pupil dilation. However, in practice, pupil dilation is still often required when using these apparatus.
While it is known that, given a large population of individuals, there can be a range of pupil sizes and a variety of pupil shapes, conventional fundus imaging apparatus are not adaptable to individual eye geometries. Instead, in practice, averaged values are used for approximating pupil size with conventional fundus imaging equipment. Little attempt is made to adapt camera operation to suit the particular characteristics of each individual eye.
In particular, the illumination optics subsystem of conventional fundus imaging apparatus is designed in such a way that it requires pupil dilation for most patients. In order to provide a truly non-mydriatic fundus imaging system that renders pupil dilation unnecessary and that can be reliably used by relatively untrained personnel, improved design of the illumination system would be required. However, the efforts of designers and manufacturers of these devices have been directed to providing more sophisticated imaging and assessment functions, many of which may actually require dilation in all cases. Thus, the limitations due to illumination subsystem design have been largely ignored and dilation is generally accepted as a requirement. For this reason, it can be seen that there is a need for an improved fundus imaging apparatus having an illumination system that allows fully non-mydriatic retinal imaging for a broad range of patients and having a set of operations tools that support non-mydriatic imaging with minimum training requirements.